This invention relates to supercritical fluid extraction and to assays of natural fats and oils, such as for example, neutral oil and loss determination for soybean and other oilseeds oils.
In supercritical fluid extraction, an extraction vessel is held at a temperature above the critical point and is supplied with fluid at pressure above the critical pressure. Under these conditions, the fluid within the extraction vessel is a supercritical fluid. In one type of apparatus for supercritical extraction, there is a specially constructed extraction vessel within a source of heat.
A prior art apparatus for supercritical extraction of this type is described by B. W. Wright, et al., in ANAL. CHEM. 59 38-44 (January, 1987) using a glass-lined extraction chamber within a bolted stainless steel extraction vessel heated in an oven. This type of extraction apparatus has the disadvantages of: (1) requiring time consuming steps to open the pressurized extraction vessel to insert the sample before use and again to open it after use to remove the spent sample; and (2) under some circumstances requiring the handling of a hot extraction vessel.
It is known how to determine or assay ratios of the components of oilseed oil to characterize the oilseed product. One method of making such an assay or determination is "neutral oil and loss determination."
In the prior art, natural oil and loss determinations are done with non-supercritical fluid extractor methods, such as for example, liquid chromatography, to estimate the amount of refinable oil present in crude oilseed oils. A liquid chromatography method, designated method CA 9f 57, for neutral oil and loss is approved by the American Oil Chemists Society.
In the method approved by the American Oil Chemists Society: (1) the oil is solubilized in an organic solvents; (2) the solubilized oil is passed through a bed of activated alumina separating medium where the polar components of the oil are absorbed; (3) the remaining solution is collected; (4) the neutral oil and loss residue solvents are removed; and (5) the value is determined by mass difference. The apparatus employed in the american Oil Chemists Society method CA 9f 57 is constructed entirely of glass with a gravity-fed solvent.
This current prior art method has several disadvantages such as: (1) large amount of organic solvents are consumed; (2) the method is time consuming; and (3) the alumina bed is prone to plugging.
Accordingly, it is an object of the invention to provide a novel supercritical fluid extraction system and method.
It is a further object of the invention to provide a two or more chambered supercritical fluid extraction cartridge separated by one or more rupture membranes.
It is a further object of the invention to provide a novel cartridge for supercritical fluid extractors.
It is a still further object of the invention to provide a novel supercritical fluid extraction system in which a multiple chamber cartridge is pressurized equally in the inside and the outside of the cartridge during extraction.
It is a still further object of the invention to provide a novel sample cartridge that can be opened and closed easily without the use of tools.
It is a still further object of the invention to provide a multiple chamber sample cartridge in which the chambers are separated by a membrane that can be easily removed and replaced.
It is a still further object of the invention to provide a novel supercritical fluid cartridge that may be reused.
It is a still further object of the invention to provide a novel cartridge for use in supercritical fluid extraction having multiple chambers and one or more separating membranes all of similar chemical makeup so that the fluid is exposed to common materials to avoid the introduction of possible reactants.
It is a still further object of the invention to provide a multiple chamber cartridge for use in supercritical fluid extraction, in which the membrane separating the chambers may be easily cleaned before use and is disposable to avoid contamination if the cartridge is reused.
It is a still further object of the invention to provide a multiple chamber cartridge for use in supercritical fluid extraction, in which the chambers are sealed by a membrane to prevent the migration of oils across, around and through the membrane prior to the beginning of fluid flow.
It is a still further object of the invention to provide a supercritical fluid extraction system in which a plurality of samples, prepared before the beginning of an extraction run and placed in a corresponding plurality of multiple-chamber sample cartridges, are automatically sequenced through the supercritical fluid extraction system with the contents of the individual chambers of each sample cartridge being isolated until pressurization of the sample cartridge within the supercritical fluid extraction system.
It is a still further object ofthe invention to provide a novel method for measuring neutral oil and loss.
It is a still further object of the invention to provide a novel method for determining or assaying the ratio of the components of oilseed using supercritical fluid extraction.
It is a still further object of the invention to provide novel apparatus useful in determining the components of certain mixtures using supercritical fluid extraction.
It is a still further object of the invention to provide cartridges for use in supercritical fluid extraction system possessing a volume of between 0.2 and 2,000 cubic centimeters.
In accordance with the above and further objectives of the invention, a supercritical fluid extraction system includes a cartridge capable of holding the sample to be extracted and a pressure vessel into which the cartridge fits. The pressure vessel fits into a heater and the cartridge is removably mounted in the pressure vessel. The pressure vessel and cartridge are held sealed by a breach plug for the pressure vessel. The sample cartridge should possess a volume of between 0.2 and 2,000 cubic centimeters and include multiple chambers which may be separated by a fluid tight membranes. Either multiple separate inlets or separate outlets are provided to permit equalization of pressure on the inside and the outside of the cartridge. In the preferred embodiment, the multiple openings are outlets to avoid contamination of extract from impurities outside of the cartridge but inside the pressure vessel.
In extracting oilseeds, a mulitple chamber cartridge may be utilized to extract the components of the oilseed. To achieve consistent results in this process, the oil and alumina are located in separate chambers of the cartridge, separated by a membrane. The membrane has a strength selected such as to rupture only upon pressurization of the inside of the cartridge This provides consistent imitation of the extraction of the neutral oil and selective deposition of the polar components of the oil onto the alumina bed and thus more predictable results.